Manufacturing edge tools and special composition of steel for same



v 6 ciency,

I Patented Oct. 4, 1927.

UNITED STATES -A ENToFF-ica.

anvnn animal) eas'ronwaornn. vow vnensacx, or noun-one naux, swnnnn.

umnracruamo EDGE roonspann sracmr. comro'sirion or .s'rnnr. iron i I No Drawing Application illed- August 2, 1926, Serial No. 126,789, and in Sweden September 1925.

The ob'ect of of manu acturing all kinds of edge tools [cutlery, surgical instruments, weapons et cetera) characterized by high cutting eflisistance to attacks of acids also a special composition of steel suitable for such edge tools.

The process is characterized thereby that loan alloy steel of the following composition and by one of the usual methods is first produced:

From 0.7 to 1.1% carbon, from 10 to 16% chromium, from 0.75 to 2.Q% manganese, the '15 remainder being iron containingthe averagepercentages oipther elements in technizaliron.

Treatment of this alloy steel is made in the usual ,way by hot rolling or forgihlg. 20 The soft condition eventually needed for the subsequent finishin can be obtained byheating the steel about 800-700 C. is. the same process as practiced in making some other special steels. i

'The, mechanical properties needed for first class cutting tools cannot, with the composition oi steel specified above, be obtained by adopting the usual hardening process. In consequence of theslight crit1-.

f cal cooling frapidity of the steel the relatively best jlesult'is obtained if the steel is p l in air from a temperature over the criticalpoilit, but the result thereby obtained is still msuflicient.

, Anbxtraordinary increase of cuttin' 'efliciency of the steel-great hardness an 'elasticity--coupled to great toughnessis obtaified the objects, hardened in air are 40 heated 'to a..tem erature of about 400 .-to

500 'C. during a out 5 to 30 minutes; thus a heat treatment'through which a hardened steel generally is lessening its hardness. After this heat treatment the grinding, polishing and sharpening follow in the usual wayv The exceptional hi h cutting eificiency of the edge tools,manu acture-d by the method above described was proved by practical tests made in comparison with tools manufactured by other-methods already known.

The tools manufactured by L the "'method which is the ob 'ect of this patent claim not only proved to esuperior to other tools of so called; stainless chromium .or chromenickel steels already known both as regards this. invention is a method even excelled great rust-resistance and great reuring several hours to Y cutting e fiiciencg and duration of edge but 1; ose made-from the purest Swedish carbon 'steel. a

Although the: cutting eflicienc of a steel so far cannot be exactly stated by figures from mechanical tests such fi res, however,

may prove tobe of someya ue forjudgingthis property:

Such figuresare so'far not'ne'arly reached by common stainless steels.

For comparison the figures for the ur'est Swedish carbon steel with "1.05% and 0.4% Mn are glven below:

- Tensile Elan .Temperins temperature g m m.

Bluctemperedn cum in on, @1480 The steel for which patent is claimed tempered at 450 C. has a Brinell hardness number of about 90 units higherthan carboh steel at about the same tensile strength and elongation; As theyelongation isa. H

measure of .the toughness it is evident from this that the newsteel with hi her hardness combines almost the same tong ass. as carbon steel is merely showing at a considerably lowerhardnes's.

It has been safel of fair quantities the metal manganese therust-r'esisting properites of the chromium steel were even increased by higher car- ?roved that by addition O bon content, Whereas the chromium and chrome-nickel steels as known lessentheir non-corrosive properties as soon as the carbon exceeds'0.8% and the chromium simultaneou sly is under 15%, the following lower limits, at which the rust-resistance is still maintained and unreduced in the high carbon chrome-manganese steel above described,

jwere fixed: g, y

1*. In steel cooled inair from high temperature; about 12% chromium.

' 2. In steel prelimina treated in the same way but afterwards re eated as above described to 400500- 0.; only about 9% chromium.

From this it is clear that the heat treatment producing the excellent cutting efficiency at the same time adds to the re sistance to corrosion.

As an example of the great rust resistance can be stated, that tools made of this steel for 6 weeks have been exposed to air-saturated river-water and moist. air without showing a single attack from rust on its surface.

Through the soft annealing the rust-resistance is more or less lost. vBy hardening in air from initially high temperature and tempering between 400 and 500 C. the rust-resistance is regained. For the rest it is the same thing with this steel as with other so called stainless steel, that the rustresistance is promoted by "a fine polished surface.

Experiments with acids showed a very high resistance to attacks of same. Diluted nitric acid and weak organic acids such as acetic acid, tartaric acid et cetera, showed only very slight effect; on the other hand the attack of warmed up and diluted hydrochloric acid took place comparatively easy.

The advantages of the new method are summarized in the following:

I. With respect to the manufacturing of the steeZ.Relatively inexpensive alloy elements (ordinary manganese iron and cheap chrgme irons of a medium carbon) could be use a H, With respect to the heat treatment- As by the method of hardening above described no abrupt changes of the temperatures are needed the risk of undue and insteel, great resistance to rust at. relatively high carbon contents and high resistance to attacks ofvarious acids Having now described my invention, what .I claim as new and desire to secure by Letters Patent is:

1. Special composition of steel, intended for the manufacture of edge tools, and characterized by the presence of the following elements: Carbon 0.71.1%, chromium 10-16%, manganese 0.7 52.0%, the remainder Fe, with the secondary elements average in technical iron.

2. Edge tools of all kinds (cutlery, surgical instruments, weapons et cetera) characterized thereby that the tools are manufactured from a composition of steel according to patent claim No. 1.

In witness whereof, I have hereunto signed my name.

ARVED EDUARD GASTON THEOPHIL von VEGESACK.

tools made from the purest Swedish carbon 

